Vol 91, No 11 (2017)

Phase equilibria in a three-component system composed of dibasic acids (hexanedioic, pentanedioic and nonanedioic) are investigated by means of differential thermal analysis. The eutectic composition is determined: 48.0 wt % pentanedioic acid, 20.0 wt % hexanedioic acid, and 32.0% nonanedioic acid. The melting temperature of the alloy is 70°C. It is concluded that this eutectic composition can be used to prepare electrolyte for thin-layer anodization.

Phase diagrams for the system water/butyric acid/propylene carbonate were plotted at T = 293.2, 303.2, 313.2 K and p = 101.3 kPa. Acidimetric titration and refractive index methods were used to determine tie-line data. Solubility data revealed that the studied system exhibits type-1 behavior of liquid–liquid equilibrium. The experimental data were regressed and acceptably correlated using the UNIQUAC and NRTL models. As a result, propylene carbonate is a suitable separating agent for aqueous mixture of butyric acid.

The results from a quantitative study of reactions between hydroxyoxo(5,10,15,20-tetraphenylporphinato)molybdenum(V) (O=Mo(OH)TPP) and 3,5-dimethylpyrazole, a biologically active base, in toluene are presented. The chemical structure and key parameters of intermediates and reaction products are determined by spectral means. The equilibrium constant (K = 51.3 L/mol) is calculated and a full kinetic description of simple reactions that occur in this system during complex transformation is obtained. The prospect of using a mixed porphyrin-containing complex as a receptor for 3,5-dimethylpyrazole, a building block for alkaloids and pharmaceutical preparations, is substantiated.

A series of Ni–La/γ-Al₂O₃ catalysts were prepared by adopting the methods of isometric impregnation and microwave impregnation. The catalysts were characterized with XRD, BET, and SEM, respectively. Inspecting the effects of adding La and the methods of impregnation on the hydrogenation activity of catalysts. The results show that adding a moderate amount of La promotes the dispersing of Ni on the carrier, the methods of microwave impregnation weaks the interaction between Ni and the carrier further, inhibits the formation of NiAl₂O₄, and the activity of catalyst prepared by the methods of microwave impregnation was significantly higher than that prepared by the methods of isometric impregnation. The hydrogenation activity of the Ni–La/γ-Al₂O₃ (WB) dipped with n(Ni): n(La) = 4: 1, microwave irradiation time 30 min with power 600W as well as calcined at 400°C exhibited the best performance. The conversion rate is 91.21% with reaction conditions: T = 160°C, p = 0.8 MPa, air speed 5 h^–1, n(H₂): n(benzene) = 2: 1.

In this paper, we selected quercetin and aromatic amino acids (tryptophan, tyrosine, phenylalanine) as the research objects to investigate the change rules in the reaction process. The thermodynamic functions (Ka, ΔG, and ΔS) of the interactions between quercetin and aromatic amino acids (tryptophan, tyrosine, phenylalanine) were measured by isothermal titration calorimetry. The values of binding constant (Ka) reached maximum at 25°C; the entropies and Gibbs free energies were both negative at different temperatures. The kinetic parameters of quercetin and amino acids in the interaction process was determined by microcalorimetry. The results inferred that the driving force of the reaction was hydrogen bond or van der Waals force.

The solubility of N₂, N₂O, and NН₃ is studied in different organic solvents. The best dissolution (0.27 ppm) is found to be for N₂O in perfluorodecalin at 291 K and a pressure of 99 kPa. The dependence of N₂O solubility in perfluorodecalin on pressure is studied at 291 K. The Gibbs energy of the solubility of nitrogen, nitrous oxide, and ammonia in perfluorodecalin is calculated.

The mean force potential (MFP) of interaction between counterions Na⁺ and Cl⁻ in a planar nanopore with structureless hydrophobic walls is calculated via computer simulation under the condition that the nanopore is in contact with water at an external pressure that exceeds the saturation pressure but remains insufficient to fill the nanopore with water. For a nanopore with a liquid phase, the MFP dependence on the interionic distance indicates the dissociation of an ion pair into two hydrated ions in a nanopore that is not completely filled with water. Fluctuations in the number of water molecules drawn into the interionic space decisively influence the dissociation. The attraction between counterions, averaged over thermal fluctuations, depends largely on the pore width and grows as the shielding of the ions’ electric field by water molecules in a narrow pore diminishes. The contributions from energy and entropy to the free energy of hydration are analyzed.

The optimized structures of some radical adducts of 5,5-dimethyl-1-pyrroline N-oxide were computed by different methods on ESR spectra. As trapped radicals, H, N₃, NH₂, CH₃, CCl₃, OOH in water and F, OH, CF₃, CH₂OH, OC₂H₅ in benzene solutions were used. The calculated isotropic hyperfine coupling constants of all the trapped radicals were compared with the corresponding experimental data. The hyperfine coupling constant due to the β proton of the nitroxide radical was seen to be consist with the McConnel’s relation α_β = B₀ + B₁cos²θ and, to be effected with the opposite spin density of oxygen nucleus bonded to the nitrogen. It was concluded that in hyperfine calculations the DFT(B3PW91)/LanL2DZ level is superior computational quantum model relative to the used other level. Also, the study has been enriched by the computational of the optimized geometrical parameters, the hyper conjugative interaction energies, the atomic charges and spin densities for all the radical adducts.

Molecular dynamic simulations of isothermal compression parameters are performed for a hexanitrohexaazaisowurtzitane single crystal (C₆H₆O₁₂N₁₂) using a modified ReaxFF-log reactive force field. It is shown that the pressure–compression ratio curve for a single C₆H₆O₁₂N₁₂ crystal at constant temperature T = 300 K in pressure range P = 0.05–40 GPa is in satisfactory agreement with experimental compression isotherms obtained for a single C₆H₆O₁₂N₁₂ crystal. Hugoniot molecular-dynamic simulations of the shock-wave hydrostatic compression of a single C₆H₆O₁₂N₁₂ crystal are performed. Along with Hugoniot temperature–pressure curves, calculated shock-wave pressure–compression ratios for a single C₆H₆O₁₂N₁₂ crystal are obtained for a wide pressure range of P = 1–40 GPa. It is established that the percussive adiabat obtained for a single C₆H₆O₁₂N₁₂ crystal is in a good agreement with the experimental data. All calculations are performed using a LAMMPS molecular dynamics simulation software package that provides a ReaxFF-lg reactive force field to support the approach.

The correlations between structural and electronic properties of the monolayer cluster Os₃ and sandwich complexes of Os₃(C₆H₆)_n (n = 1, 2) were studied with density functional theory. Every Os adopts η² fashion to coordinate with C₆H₆ in Os₃(C₆H₆), while every Os adopts η² and η¹ fashion to coordinate with below and above C₆H₆ rings in Os₃(C₆H₆)₂. η² fashion is σ donation and π back bond, and η¹ fashion belong to σ bond. The first binding energy between Os₃ and below C₆H₆ ring is–114.23 kJ/mol, which is weaker than the second binding energy with–174.16 kJ/mol between Os₃(C₆H₆) and above C₆H₆ ring. The reason is that the change of spin multiplicity is different, which leads the symmetry of Os₃(C₆H₆)₂ to be broken.

The magnetic property and electronic properties such as binding energy, charge transfer, ionization potential and electron affinity of the Ni_n–1Ge (n = 13–23) neutral and ionic clusters have been studied using the density functional theory calculations with the PBE exchange-correlation energy functional. The calculated total magnetic moments decrease with the addition of Ge atom. Both the calculated ionization potential and electron affinity exhibit an oscillating behavior as the cluster size increases.

New hybrid materials based on Pt, Fe, and Pt–Fe nanoparticles stabilized in a matrix of polymethylsilsesquioxane nanogel and ultrahigh molecular weight polyethylene (UHMWPE) were prepared. Metal vapor synthesis was used to produce mono- and bimetallic nanoparticles. It was shown that organosilicon nanogel effectively stabilizes Pt nanoparticles with an average size of 0.9 nm. Using the nanogel results in the formation of superparamagnetic Fe particles 3–5 nm in size that consist of ferromagnetic Fe⁰ core and antiferromagnetic shells of Fe oxides. It is established that using an organosilicon matrix in the formation of Pt-Fe/UHMWPE systems helps reduce the average particle size of Fe in the material from 6.5 to 4.5 nm and narrow their particle size distribution. The composition, magnetic and electronic characteristics of the nanocomposites are studied via transmission electron microscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, XANES, and EXAFS.

The structural, optical and catalytic properties of undoped (CuO–ZnO) and CdS doped CuO–ZnO (CdS/CuO–ZnO) nanoparticles were studied. The blue shifting of optical band gap in CuO–ZnO nanoparticles as compared to their respective bulk oxides (CuO: 1.21–1.5 eV, ZnO: 3.37 eV) was observed as 3.9 eV, while red shifting after doping of CdS was found from 3.9 to 3.7 eV. The angle of diffraction and FWHM values were used to observe crystallite phase and to calculate crystallite size (using Scherer and Williamson–Hall equations) and other parameters like strain, dislocation density and bond length of nanoparticles. The particle size of CuO–ZnO and CdS/CuO–ZnO nanoparticles using transmission electron microscopy (TEM) was found 12.54 and 6.93 nm, respectively. It was concluded that decrease in particle size cause red shifting which increase the catalytic efficiency of nanoparticles.

A molecular theory based on the lattice gas model (LGM) is used to calculate the surface tension of one- and two-component planar vapor–liquid interfaces of simple fluids. Interaction between nearest neighbors is considered in the calculations. LGM is applied as a tool of interpolation: the parameters of the model are corrected using experimental surface tension data. It is found that the average accuracy of describing the surface tension of pure substances (Ar, N₂, O₂, CH₄) and their mixtures (Ar–O₂, Ar–N₂, Ar–CH₄, N₂–CH₄) does not exceed 2%.

The effect the flow rate of a mobile phase has on the frontal dynamics of antibiotic erythromycin sorption by monolithic molecularly imprinted polymeric sorbents based on 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate and their non-imprinted analog is studied. It is shown that erythromycin sorption proceeds in both the interglobular and intraglobular space of monolithic matrices, and the dynamic capacity of sorption can be regulated by changing the time of the experiment. The mobile phase flow rate at which the maximum specific bonding of the antibiotic by molecularly imprinted monolithic sorbents is observed is determined.

The kinetics of the sorption of vanillin by a granulated anion exchanger is studied under static conditions. A comparison of the kinetic curves of the uptake of hydroxybenzaldehyde by gel and macroporous anion exchanger shows that macroporous sorbent has better kinetic characteristics. The effect temperature has on the capacity of an anion exchanger and the time needed to establish sorption equilibrium is found, and the activation energy of vanillin uptake is determined. Studying the effect experimental factors have on the rate of sorption and using the formal kinetics approach, it is established that in the investigated range of concentrations, the limiting stage of the uptake of vanillin by an anion exchanger with the functional groups of a quaternary ammonium base is that of external diffusion. Vanillin sorption by a highly basic anion exchanger in hydroxyl form is characterized by polymolecular uptake best described by a BET isotherm; at the same time, the uptake of sorbate by a chloride form is of a monomolecular character and can be described by a Freindlich isotherm. Structural changes in the anion exchanger sorbed hydroxybenzaldehyde are identified via FTIR spectroscopy.

The change in entropy at the nodes of the a separation cascade during the processing of a multicomponent mixture is calculated. A thermodynamic interpretation of the nature of the difference between the work of the cascade, determined from the separation potential and the thermodynamically estimated work of the isobaric–isothermal mixing of the fractions released at its ends, is presented.

The solubilization of hydrophobic porphyrin photosensitizers (PPSes) to obtain corresponding water-soluble forms is an important line of modern antimicrobial photodynamic therapy. It is shown that a triblock copolymer of ethylene and propylene oxides, Pluronic F-127, one of the most nontoxic and effective polymer surface active substances (SASes), can be used for the conversion of hydrophobic tetraphenylporphyrin (TPP) and monosubstituted and tetrasubstituted hydroxy, amino, and nitro TPPs into water-soluble forms. It is found that Pluronic has a substantially higher solubilizing affinity (defined as the minimum molar concentration of an SAS required for the complete migration of porphyrin with a specific molar concentration to the aqueous phase) toward monosubstituted TPPs than to corresponding tetrasubstituted porphyrins. It is shown that with Pluronic in the organic phase, the activity of tetraphenylporphyrin in a test reaction of the oxidation of anthracene is higher than that of its monosubstituted and tetrasubstituted derivatives. In an aqueous medium, the activity of solubilized mono derivatives of TPP is comparable to that of unsubstituted TPP and is higher than the activity of the corresponding tetra derivatives of TPP.

Components of the tensor of the electron polarizability of molecules of carboxylic acids and their dimers and trimers with conjugated chemical bonds are calculated according the Hartree–Fock method. The dependences of a change in the anisotropy of polarizability on the average polarizability of a molecule and the number of electrons in a conjugated system are determined. An increase in the anisotropy of electron polarizability during the formation of intermolecular associates through hydrogen bonds is observed.

The microwave spectrum of 2-methyltetrahydrofuran in the ground vibrational state is studied. Rotational transitions belonging to one conformer of the molecule are found; no lines belonging to other conformers are detected in the spectrum. Such spectroscopic parameters of a molecule as rotational and quartic centrifugal distortion constants are determined using a set of identified rotational transitions in the quasirigid rotor approximation. Components of the dipole moment of a molecule in the principal axes system are determined from the Stark effect for four rotational transitions. Stable conformations of the molecule are sought by means of B3PW91 and B3LYP with aug-cc-pVXZ (X = D, T, Q) basis sets. A possible stable conformation of the molecule is discussed.

A serious of carbon loaded Pd–Cr bimetallic catalysts (Pd_xCr_1–x/C, x = 0.6–1, atomic ratio) were prepared by chemical reduction method. Among them, Pd_0.8Cr_0.2/C catalyst exhibits the highest catalytic activity for oxygen reduction reaction. Its activity is higher than that of Pd/C and previously reported Pd_0.61Cr_0.39. Due to the stability of Cr, the Pd_0.8Cr_0.2/C exhibit excellent durability during electrochemical measurements, which indicates that Pd_0.8Cr_0.2 is a potential candidate for the cathode of proton exchange membrane fuel cells.

Reference no. 13 should read: 13. O. S. Brovko, I. A. Palamarchuk, T. A. Boitsova, et al., Macromol. Res. 23, 1057 (2015).